Selection of coefficients for quantization processing based on whether an original image is a still image or a moving image

ABSTRACT

The present invention permits to determine an image characteristic amount for efficiently searching an image without affecting a bad influence upon searching accuracy. First image characteristic amount data is extracted. Second image characteristic amount data is extracted. Then, a distance between two image characteristic amount data is calculated. Further, the calculated distance is compared with a threshold value. If the distance is smaller than the threshold value, the image characteristic amount data having smaller number of coefficients which is advantageous because of smaller data amount is selected, and, if otherwise, the image characteristic amount data having greater number of coefficients is selected.

This application is a divisional of U.S. application No. 09/977,318,filed on Oct. 16, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image processing method capable ofprocessing an image, and an apparatus therefor.

2. Description of the Related Art

It is known to provide a system in which an image is scaled, and aresulting scaled image is subjected to known discrete cosine transform(DCT) processing and quantization processing to obtain pluralcoefficients from which several coefficients are picked up from lowfrequency component side, and the picked-up coefficients is regarded asa characteristic amount for an original image and is used as data forsearching the image (refer to ISO/IEC JTC1/SC29/WG11/N3522 “MPEG-7Visual Working Draft 4.0” ([VWD 4.0]) or ISO/IEC JTC1/SC29/WG11/N3522“MPEG-7 Visual part of experimentation Model Version 7.0” ([VXM 7.0]).

FIG. 1 is a view showing characteristic data extracting processing inColor Layout descriptor described in the above document [VWD 4.0] or[VXM 7.0]. Further, FIG. 8 is a flow chart showing such processing.

An original image 10001 is scaled down into 8×8 pixels (step S10401),and each pixel of resulting 8×8 pixel images (10011, 10012, 10013) isconverted into Y/Cb/Cr color space data (10021, 10022, 10023) (stepS10402). Then, Y, Cb and Cr data components 10021, 10022, 10023 aresubjected to DCT processing step 10403) to obtain DCT coefficients10031, 10032, 10033, and the coefficients 10031, 10032, 10033 aresubjected to quantization processing (step S10404).

The image scaling processing, color conversion processing and DCTconversion processing may be well-known ones.

For example, according to [VWD 4.0], the quantization processing can berealized by processing shown in the following program codes 10000-10003.The program codes 10000-10003 are described by using well-known Clanguage. According to the above document, in the quantizationprocessing, since different processing operations are effected for a DCcomponent and an AC component with respect to Y component and Cb/Crcomponents, the above document presents four program codes 10000-10003for the quantization processing. Program code 10000: Quantizationprocessing for DC component of Y coefficient

Int quant_Y_DC(int i)  int j ;  i = i/8;  if(i>192)j= 1 1 2+(i−192)/4; else if(i>160)j=96+(i−160)/2;  else if(i>96)j=32+i−96;  elseif(i>64)j=16+(i−64)/2;  else j=i/4;  return j>>1; }Program code 10001: Quantization processing for DC component of Cb/Crcoefficients

Int quant_CbCr_DC(int i)  int j;  i=i/8;  if(i>191)j=63; elseif(i>160)j=56+(i−160)/4;  else if(i>144)j=48+(i−144)/2;  elseif(i>112)j=16+ I −112;  else if(j>96)j=8+(i−96)/2;  elseif(i>64)j=(i−64)/4;  else j=i/0;Program code 10002: Quantization processing for AC component of Ycoefficient

Int quant_Y_AC(int i) {  int j;  i=i/2;  if(i>255)I=255; if(i<−256)I=−256;  if(abs(i)>127)j=64+abs(i)/4;  elseif(abs(i)>63)j=32+abs(i)/2;  else j=abs(i);  j=(i<0)?−j:j; return(int)trunc(((double)j+128.0)/8.0+0.5); }Program code 10003: Quantization processing for AC component of Cb/Crcoefficients

Int quant_CbCr_AC(int i){  int j;  if(i>255)I=255;  if(i<−256)i=−256; if(abs(i)>127)j=64+abs(i)/4;  else if(abs(i)>63)j=32+abs(i)/2;  elsej=abs(i);  j=(i<0)?−j:j;  return(int)trunc(((double)j+128.0)/8.0+0.5); }

As a result of the quantization processing using the program codes 10000and 10001, the quantization-processed DCT coefficients (refer to as“quantization DCT coefficients” hereinafter) of Y or Cb/Cr componentshave values between 0 and 64. Further, as a result of the quantizationprocessing using the program codes 10002 and 10003, the quantization DCTcoefficients of Y or Cb/Cr components have values between 0 and 32.

Accordingly, the DC component of the quantization DCT coefficient can berepresented by 6 bits (no sign) and the AC component can be representedby 5 bits (no sign).

Further, among the quantization DCT coefficient 10041, 10042, 10043obtained by the quantization processing, several coefficients areselected from a low frequency component side (step S10405). In case ofFIG. 4, as an example, six coefficients are selected regarding the Ycomponent coefficients and three coefficients are selected regardingeach of the Cb/Cr component coefficients. The selection of thecoefficients is actually realized by re-placing coefficients arranged8×8 two-dimensional pattern into coefficients arranged in aone-dimensional pattern by means of a zigzag scan shown in FIG. 1 andselecting several leading coefficients from the one-dimensional pattern.The reference numeral 10101 in FIG. 5 shows the zigzag scan. Numbersfrom 1 to 64 written in blocks of the scan 10101 represent orders (froma leading order (1)) of the related coefficients after they werere-placed into the one-dimensional pattern.

Lastly, several coefficients are picked up from a low frequencycomponent side. According to [VWD 4.0], the number of coefficientspicked up here is 1, 3, 6, 10, 15, 21, 28 or 64. Further, although thenumber of the Cb component coefficients is the same as that of the Crcomponent coefficients, the number of the Y component coefficients maybe differentiated from the number of the Cb/Cr component coefficients.According to [VWD 4.0], regarding default, six Y component coefficientsand three Cb/Cr component coefficients are selected. In FIG. 4, as anexample, six Y component coefficients (10051) and three Cb/Cr componentcoefficients (10052, 10053) are selected as coefficients in the default.

The selected coefficients 10051, 10052, 10053 are used as characteristicdata of the original image 10001, i.e., Color Layout descriptor data.

Further, according to [VWD 4.0], the Color Layout descriptor is storedin a form of a binary structure as shown in FIG. 6 or FIG. 7. In thestructure 10201 of FIG. 6 and the structure 10301 of FIG. 7, each squareblock represents one bit. Further, in the structures 10201, 10301,although items are written in partition from field to field for theconvenience of explanation, actually, the items are continuously storedin an order as shown by the broken lines in FIG. 6 and FIG. 7.

FIG. 6 is a view showing the binary structure when Color Layoutdescriptor is default, i.e., when the number of Y quantization DCTcoefficients is six and the number of Cb/Cr quantization DCTcoefficients is three. In this case, “0” is stored in a leadingextension flag. Following to this, six Y quantization DCT coefficients,three Cb quantization DCT coefficients and three Cr quantization DCTcoefficients are stored in order. As mentioned above, as a result ofquantization, regarding the quantization DCT coefficient, since the DCcomponent can be represented by 6 bits (no sign) and the AC componentcan be represented by 5 bits (no sign), the DC component is stored in a6-bits area and the AC component is stored in a 5-bits area.

On the other hand, FIG. 7 is a view showing the binary structure whenColor Layout descriptor is not default. In this case, “1” is stored in aleading extension flag. This is followed by two 3-bits areas. These3-bits areas are used for representing the number of Y quantization DCTcoefficients and the number of Cb/Cr quantization DCT coefficients,respectively.

TABLE 10001 Bit pattern for coefficient designating field and meaningthereof Number of quantization Bit pattern DCT coefficients 000 1 001 3010 6 011 10 100 15 101 21 110 28 111 64

Following to these two 3-bits coefficient designating fields, Y, Cb andCr quantization DCT coefficients are stored in order. The numbers of theY, Cb and Cr coefficients are the numbers of coefficients designated bythe above-mentioned coefficient designating fields. In 10301 of FIG. 7,as an example, the number of Y quantization DCT coefficients is six andthe number of Cb/Cr quantization DCT coefficients is six.

Further, according to [VXM 7.0], similarity between the characteristicdata is calculated the following equation. For example, similarity Dbetween two Color Layout descriptors, i.e., CLD1 (Y Coeff, Cb Coeff, CrCoeff) and CLD2 (Y Coeff′, Cb Coeff′, Cr Coeff′) is calculated by thefollowing equation 10001:

$D = {\sqrt{\sum\limits_{i = 0}^{{{Max}({NumberOfYCoeff}\;)} - 1}{\lambda_{Yi}( {{{YCoeff}\lbrack i\rbrack} - {{YCoeff}^{\;\prime}\lbrack i\rbrack}} )}^{2}} + \sqrt{\sum\limits_{i = 0}^{{{Max}({NumberOfYCCoeff}\;)} - 1}{\lambda_{Cbi}( {{{CbCoeff}\lbrack i\rbrack} - {{CbYCoeff}^{\;\prime}\lbrack i\rbrack}} )}^{2}} + \sqrt{\sum\limits_{i = 0}^{{{Max}({NumberOfYCCoeff}\;)} - 1}{\lambda_{Cri}( {{{CrCoeff}\lbrack i\rbrack} - {{CrCoeff}^{\;\prime}\lbrack i\rbrack}} )}^{2}}}$

In the above equation 10001 for calculating Color Layout descriptor, λis weighting regarding the respective coefficients, and, in [VXM 7.0],weighting values shown in the following Table 10002 are described:

TABLE 10002 Weighting values in equation 10001 Order of coefficient 1 23 4 5 6 Y 2 2 2 1 1 1 Cb 2 1 1 Cr 4 2 2

Further, if the numbers of coefficients included in two descriptors aredifferent, the equation 10001 is applied to the fewer number, or value“16” is supplemented to the deficient number and the equation 10001 isapplied to the higher number.

Regarding the selection of the numbers of quantization DCT coefficientsincluded in Color Layout descriptor, in case of default, six is selectedfor Y and three is selected for Cb/Cr. Normally, it was required thatsuch a coefficient selecting method is uniformly determined in a systemby predetermining it by the system or is designated by the user case bycase.

However, the default coefficient selecting method is not alwaysall-around and is not sufficient to represent characteristics of all ofimages. If insufficient, searching accuracy of the entire searchingsystem will be subjected to a bad influence.

On the other hand, to avoid this, it is considered that selection ofcoefficients is effected to obtain more coefficient data or allcoefficient data are held. In this case, however, a characteristicamount data size naturally becomes bulky. This may lead to anundesirable case in which the number of images to be treated increasedgreatly or data capacity is severely limited by a storing area or acommunication path.

Accordingly, in order to efficiently utilize Color Layout descriptorwithout affecting a bad influence upon the searching accuracy, thenumber of quantization DCT coefficients held for each image must bedetermined suitably.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is providedan image processing apparatus comprising first extracting means forextracting a first image characteristic amount from an image, secondextracting means for extracting a second image characteristic amountfrom the image, judging means for judging similarity between the firstimage characteristic amount extracted by the first extracting means andthe second image characteristic amount extracted by the secondextracting means, and selecting means for selecting either the firstimage characteristic amount or the second image characteristic amount asa characteristic amount of the image in accordance with a judging resultof the judging means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing characteristic data extraction processing;

FIG. 2 is a view showing processing in comparison between descriptorshaving different numbers of coefficients;

FIG. 3 is a flow chart showing coefficient selection judgementprocessing;

FIG. 4 is a view showing characteristic extraction processing for ColorLayout descriptor;

FIG. 5 is a view showing zigzag scanning processing;

FIG. 6 is a view showing a binary storing system (in default) for ColorLayout descriptor;

FIG. 7 is a view showing a binary storing system for Color Layoutdescriptor;

FIG. 8 is a flow chart showing the characteristic extraction processingfor Color Layout descriptor; and

FIG. 9 is a block diagram showing a construction of an image processingapparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be explained in connection withembodiments thereof with reference to the accompanying drawings.

First Embodiment

FIG. 9 is a block diagram showing a construction of an image processingapparatus capable of effecting image characteristic amount extractionprocessing according to a first embodiment of the present invention.

In FIG. 9, a data input/output portion 900 is an image inputting devicecapable of inputting both still image data and moving image data. Morespecifically, such a portion is a digital video device capable ofeffecting still image sensing. Further, data such as an imagephoto-taken by a digital camera can be read-in from a memory card or aPC card through USB. Conversely, data such as an image can be written inthe memory card.

An input portion 901 is a device for inputting instruction from the useror data and includes a keyboard and a pointing device. Incidentally, thepointing device may be a mouse, a track ball or a tablet. A concreteexample of the input portion 901 may include mode setting means forsetting an image input mode or an image sensing mode.

A storage portion 902 is a device for storing image data or imagecharacteristic amount data, and, normally, a hard disk and the like isused. A display portion 903 is a device for displaying an image such asGUI, generally, CRT or a liquid crystal display and the like is used.

A CPU 904 is associated with all of processing operations. A ROM 905 anda RAM 906 serve to provide programs required for the processingoperations, data and a working area to the CPU 904. Further, controlprograms required for processing operation shown in flow charts of FIGS.3 and 8 are stored in the storage portion 902 or in the ROM 905.Incidentally, when the control program is stored in the storage portion902, after the program is read-in in the RAM 906 once, the program isexecuted. Incidentally, regarding the construction of the system,although there are various constructions other than the above-mentionedone, since the construction of the system does not form a subject matterof the present invention, explanation thereof will be omitted.

Now, an image characteristic amount extracting system using theabove-mentioned image processing apparatus will be explained withreference to the accompanying drawings.

First of all, since general flow of image characteristic amountextraction of Color Layout descriptor is the same as the prior art andis as shown in FIGS. 4, 5 and 6, explanation thereof will be omittedhere.

In the prior art, although Y, Cb, Cr data were obtained by effectingcolor conversion after the original image was scaled down, in thepresent invention, it is sufficient to have Y, Cb, Cr data for 8×8pixels as input for DCT processing, and, for example, the presentinvention also includes the fact that the entire original image issubjected to color conversion, and, thereafter, Y, Cb, Cr data for 8×8pixels are obtained by a conventional image scaling system. Furthermore,when the original image is image data of Y/Cb/Cr type, color conversionis complicated, and the present invention can be carried out even if thecolor conversion is omitted.

Hereinbelow, for simplicity's sake of explanation, it is assumed thatColor Layout descriptor for holding x (in number) quantization DCT for aY component, y (in number) quantization DCT for a Cb component and z (innumber) quantization DCT for a Cr component is referred to as x/y/zdescriptor.

Now, it is considered to form Color Layout descriptor for a certainimage. For example, as shown in FIG. 1, two coefficient selectingsystems of 6/3/3 and 6/6/6 type are prepared, and one of them isselected.

FIG. 1 is a view showing coefficient selection for the imagecharacteristic amount data of a certain image. In FIG. 1, the referencenumeral 101 denotes (a part of) quantization DCT coefficient of a Ycomponent; 102 denotes (a part of) quantization DCT coefficient of a Cbcomponent; and 103 denotes (a part of) quantization DCT coefficient of aCr component. A method for obtaining quantization DCT coefficientsregarding 101 to 103 is shown in FIG. 4.

As shown in 111-113 of FIG. 1, these coefficients are arranged in aone-dimensional pattern by zigzag scanning processing as shown in FIG.5.

Then, the coefficient selection is effected on the basis of thequantization DCT coefficients arranged in the one-dimensional pattern.Here, for example, when the selection is effected by using 6/3/3 type, aset of coefficients 121 shown in FIG. 1 are extracted. Alternatively,when the selection is effected by using 6/6/6 type, a set ofcoefficients 122 shown in FIG. 1 are extracted;

If the characteristic represented by the set 121 of quantizationcoefficients is well similar to the characteristic represented by theset 122 of quantization coefficients, the set 121 of quantizationcoefficients is advantageous since the data amount is smaller.Conversely, if the characters are not so similar to each other, the set121 of quantization coefficients may have possibility of deficiency of apart of characteristic of the original image. Accordingly, the selectionis effected on the basis of a certain reference or standard.

To effect the selection, in the illustrated embodiment, a distancebetween the set 121 of quantization coefficients and the set 122 ofquantization coefficients is considered. According to [VXM 7.0], in thecalculation of distance of descriptor, there is shown a method in which,if the numbers of coefficients of the descriptors to be compared isdifferent, a part of the coefficient of descriptor having greatercoefficients is neglected to match it to the descriptor having smallercoefficients or 16 is supplemented to the coefficient portion which isnot included in the descriptor having smaller coefficients to match itto the descriptor having greater coefficients.

In the former case, when the part of coefficients are removed from theset 121, the sets 121, 122 becomes always the same. However, in thelatter case, depending upon the values of Cb4-Cb6 and Cr4-Cr6, the sets121, 122 do not coincide with each other. A set 121′ in FIG. 2represents a set obtained by supplementing 16 to the lacked componentsof the set 121.

In the illustrated embodiment, a distance between the set 121′ and theset 122 is considered. If the distance therebetween is very small, it isconsidered that the characteristics of the original images representedby these sets are very similar to each other. In such a case, the set121 (6/3/3) which is advantageous because of smaller data amount isselected. If otherwise, the set 122 is selected.

As distance between the sets 121′ and 122, various factors can beconsidered. In the illustrated embodiment, a total of absolutedifference between corresponding coefficients of the set 121′, 122 isconsidered. That is to say, “d” in the following equation is considered:

$d = {{\sum\limits_{i = 1}^{NumberOfY}{{{Yi} - {Y^{\prime}i}}}} + {\sum\limits_{j = 1}^{NumberOfCb}{{{Cbi} - {{Cb}^{\prime}j}}}} + {\sum\limits_{k = 1}^{NumberOfCr}{{{Crk} - {{Cr}^{\prime}k}}}}}$Equation 1: an example (1) for measuring the distance between twodescriptors according to the present invention.

Where, in case of the sets 121′ and 122,

-   -   Yi=Y′i (1≦i≦6)    -   Cbj=Cb′j (1≦j≦3)    -   Crk=Cr′k (1≦k≦3)    -   Cb′j=Cr′k=16 (4≦k≦6)        are satisfied. Here, Y′i, Cb′j and Cr′k represent the        coefficients of the set 122, and Yi, Cbj and Crk represent the        coefficients of the set 121′. When these values are substituted,        the equation (1) becomes as follows:

$d = {{\sum\limits_{j = 3}^{6}{{16 - {{Cb}^{\prime}j}}}} + {\sum\limits_{k = 1}^{6}{{16 - {{Cb}^{\prime}k}}}}}$Equation 2: an example (2) for measuring the distance between twodescriptors according to the present invention

Then, the value d is compared with a predetermined threshold value Th.If the value d is smaller than the value Th, it is judged that the sets121′ and 122 are sufficiently similar to each other, and the set 121(i.e., the quantization DCT coefficients of 6/3/3 type) is selected. Ifotherwise, the set 122 (i.e., the quantization DCT coefficients of 6/6/6type) is selected. The threshold value may be any positive value.Further, the threshold value may be dynamically determined under acertain condition or may be previously determined by an experientialmethod.

In the illustrated embodiment, while an example that the total of theabsolute difference between the corresponding coefficients is used forjudging the distance between two descriptors was explained, the distancemay be defined in another way. For example, the distance may be definedin accordance with the above-mentioned [VXM 7.0]. Further, while thejudgement was effected by using the single equation, for example, thejudgement processing regarding Y, Cb and Cr color components may beeffected and the judgement may be effected in accordance with “and”condition and “or” condition thereof.

In the illustrated embodiment, while an example that 6/6/6 type and6/3/3 type are prepared as candidates of the numbers of quantization DCTcoefficients was explained, other types or patterns may be used.

FIG. 3 is a flow chart showing the coefficient selection judgementprocessing.

First of all, in a step S301, the first image characteristic amount datais extracted. In the illustrated embodiment, this corresponds to theextraction processing for extracting the set 121, for example. Then, ina step S302, the second image characteristic amount data is extracted.In the illustrated embodiment, this corresponds to the extractionprocessing for extracting the set 122, for example.

Then, in a step S303, the distance between two image characteristicamount data is calculated. That is to say, in the illustratedembodiment, the set 121′ is formed from the set 121 of quantization DCTcoefficients and the distance d between the sets 121′ and 122 iscalculated on the basis of the equation 1 or equation 2, for example.

Further, the calculated distance d is compared with the threshold valuein a step S304. If the distance d is smaller than the threshold value,the image characteristic amount data which is advantageous because ofsmaller number of coefficients is selected (step S305). If otherwise,the image characteristic amount data having greater number ofcoefficients is selected.

Then, Color Layout descriptor is formed by using the selectedquantization DCT coefficients.

Second Embodiment

In the first embodiment, while an example that the number ofquantization DCT coefficients is determined in accordance with the valueof the descriptor data was explained, such number may be altered inaccordance with an image sensing condition.

For example, experientially, it was found that moving image data has arelatively small dynamic range and can be well represented by 6/3/3type. On the other hand, it was found that many of the still images arehigh fine images and frequently cannot be well represented unless 6/6/6type is used.

Thus, in a second embodiment of the present invention, in the selectionbetween 6/3/3 type and 6/6/6 type is determined in accordance with theimage sensing condition of the original image. That is to say,

-   -   when the original image is the moving image, quantization DCT        coefficients of 6/3/3 type is selected; and    -   when the original image is the still image, quantization DCT        coefficients of 6/6/6 type is selected.        The judgement whether the original image is the moving image or        the still image may be effected on the basis of MINE TYPE of the        original image data, a file name or an extension element, and        for example, when the present invention is applied to a        conventional digital video device capable of image sensing both        the moving image and the still image, such judgement may be        effected on the basis of an image sensing mode (designated by        the user through a dial, for example).

Incidentally, the present invention may be applied to a systemconstituted by plural equipments (for example, host computer, interfacedevice, reader, printer and the like) or a device constituted by asingle equipment (for example, copying machine, facsimile or the like).

Further, it should be noted that the object of the present invention canbe achieved by supplying a storing medium storing a program code ofsoftware for executing the functions of the above-mentioned embodimentsto the system or the apparatus and by reading out and executing theprogram code stored in the recording medium by means of a computer (orCPU or MPU) of the system or the apparatus.

In this case, the program code itself read out from the recording mediumrealizes the functions of the embodiments, and, thus, the storing mediumstoring such program code constitutes the present invention.

As the storing medium for storing the program code, for example, afloppy disk, a hard disk, an optical disk, a photo-magnetic disk,CD-ROM, CD-R, a magnetic tape, a non-volatile memory card or ROM can beused.

Further, it should be noted that the present invention includes aconcept that not only the functions of the above-mentioned embodimentsare realized by executing the program code read out by means of thecomputer, but also OS (operating system) running on the computerexecutes the actual processing partially or totally on the basis ofinstruction of the program code to realize the functions of theembodiments.

Further, it should be noted that the present invention includes aconcept that, after the program code read out from the storing medium iswritten in a memory of a function extension board inserted into thecomputer or a function extension unit connected to the computer, a CPUof the function extension board or of the function extension unitexecutes the actual processing partially or totally on the basis ofinstruction of the program code to realize the functions of theembodiments.

As mentioned above, in the image characteristic amount extracting systemin which several coefficients are selected and extracted among thequantization DCT coefficients obtained by effecting the discrete cosinetransform and quantization processing with respect to the image having8×8 pixels from the low frequency component side and the extractedcoefficients are used as the characteristic amount of the originalimage, the preferable number of coefficients can be selected by alteringthe number of coefficients to be extracted in accordance with theoriginal image.

The image characteristic amount for efficiently searching the image canbe determined without affecting a bad influence upon the searchingaccuracy.

1. An image processing apparatus comprising: DCT processing means foreffecting DCT processing of an image which is represented by Y/Cb/Crcolor space; quantization means for effecting quantization of datasubjected to the DCT processing by said DCT processing means; judgingmeans for judging whether an original image is a moving image or a stillimage; coefficient selecting means for selecting a number ofquantization DCT coefficients to be extracted from among thequantization DCT coefficients subjected to the quantization by saidquantization means, in accordance with a judging result by said judgingmeans; and setting means for setting the number of quantization DCTcoefficients selected by said coefficient selecting means as an imagecharacteristic amount; wherein the quantization DCT coefficients ofY/Cb/Cr components are re-arranged by zigzag scanning, and, when theoriginal image is a still image, greater than or equal to sixquantization DCT coefficients of a Y component and greater than or equalto three quantization DCT coefficients of Cb/Cr components are selected,respectively, from a low frequency component side, and, when theoriginal image is a moving image, six quantization DCT coefficients ofthe Y component and three quantization DCT coefficients of the Cb/Crcomponents are selected, respectively, from a low frequency componentside.
 2. An image processing apparatus according to claim 1, wherein theimage has 8×8 pixels.
 3. An image processing apparatus according toclaim 2, wherein the image having 8×8 pixels is obtained by scaling downthe original image and by converting it into Y/Cb/Cr color space data.4. An image processing apparatus according to claim 1, furthercomprising extracting means for extracting several quantization DCTcoefficients from the low frequency component side on the basis of thequantization DCT coefficients selected by said coefficient selectingmeans.
 5. An image processing apparatus according to claim 1, furthercomprising image inputting means capable of inputting both still imagedata and moving image data.
 6. An image processing apparatus accordingto claim 5, wherein said image inputting means, capable of inputtingboth still image data and moving image data, is a digital video devicecapable of effecting still image sensing, and the number of quantizationDCT coefficients to be selected is based on an image sensing mode of thedigital video device.
 7. An image processing apparatus according toclaim 5, wherein MIME TYPE of data including the original image judgeswhether the original image has still image data or moving image data. 8.An image processing apparatus according to claim 5, wherein said judgingmeans judges whether the original image has still image data or movingimage data based on a file extension of a data file including theoriginal image.
 9. An image processing apparatus comprising: DCTprocessing means for effecting DCT processing of an image; quantizationmeans for effecting quantization of data subjected to the DCT processingby said DCT processing means; judging means for judging whether anoriginal image is a moving image or a still image; coefficient selectingmeans for selecting a number of quantization DCT coefficients to beextracted from among the quantization DCT coefficients subjected to thequantization by said quantization means, in accordance with a judgingresult by said judging means; and setting means for setting the numberof quantization DCT coefficients selected by said coefficient selectingmeans as an image characteristic amount, wherein two candidates areprepared as the number of quantization DCT coefficients by saidselecting means, one is selected among them, and a similarity betweenfirst image characteristic amount data associated with the smallernumber of quantization DCT coefficients and second image characteristicamount data associated with the greater number of quantization DCTcoefficients is judged, and one of the first image characteristic amountdata and the second image characteristic amount data is selected inaccordance with a comparison result between a similarity value and apredetermined threshold value, wherein, when the similarity between thefirst image characteristic amount data and the second imagecharacteristic amount data is judged, judgement of the similarity iseffected by supplementing a predetermined value as data of a coefficientportion which is not included in the first image characteristic amountdata having a smaller number of coefficients but is included in thesecond image characteristic amount data having a greater number ofcoefficients to the first image characteristic amount data, and whereinthe predetermined value is 16 which is the number of quantization DCTcoefficients.
 10. An image processing method comprising: a DCTprocessing step of effecting DCT processing of an image which isrepresented by Y/Cb/Cr color space; a quantization step of effectingquantization of data subjected to the DCT processing in said DCTprocessing step; a judging step of judging whether an original image isa moving image or a still image; a coefficient selecting step ofselecting a number of quantization DCT coefficients to be extracted fromamong the quantization DCT coefficients subjected to the quantization insaid quantization step, in accordance with a judging result by saidjudging step; and a setting step of setting the number of quantizationDCT coefficients selected in said coefficient selecting step as an imagecharacteristic amount; wherein the quantization DCT coefficients ofY/Cb/Cr components are re-arranged by zigzag scanning, and, when theoriginal image is a still image, greater than or equal to sixquantization DCT coefficients of a Y component and greater than or equalto three quantization DCT coefficients of Cb/Cr components are selected,respectively, from a low frequency component side, and, when theoriginal image is a moving image, six quantization DCT coefficients ofthe Y component and three quantization DCT coefficients of the Cb/Crcomponents are selected, respectively, from a low frequency componentside.
 11. An image processing method according to claim 10, wherein theimage has 8×8 pixels.
 12. An image processing method according to claim11, wherein the image having 8×8 pixels is obtained by scaling down theoriginal image and by converting it into Y/Cb/Cr color space data. 13.An image processing method according to claim 10, further comprising anextracting step of extracting several quantization DCT coefficients fromthe low frequency component side on the basis of the quantization DCTcoefficients selected in said coefficient selecting step.
 14. An imageprocessing method according to claim 10, further comprising an imageinputting step capable of inputting both still image data and movingimage data.
 15. An image processing method according to claim 14,wherein MIME TYPE of data including the original image judges whetherthe original image has still image data or moving image data.
 16. Animage processing method according to claim 14, wherein said judging stepincludes judging whether the original image has still image data ormoving image data based on a file extension of a data file including theoriginal image.
 17. An image processing method comprising: a DCTprocessing step for effecting DCT processing of an image; a quantizationstep of effecting quantization of data subjected to the DCT processingin said DCT processing step; a judging step of judging whether anoriginal image is a moving image or a still image; a coefficientselecting step of selecting a number of quantization DCT coefficients tobe extracted from among the quantization DCT coefficients subjected tothe quantization in said quantization step, in accordance with a judgingresult by said judging step; and a setting step of setting the number ofquantization DCT coefficients selected in said coefficient selectingstep as an image characteristic amount, wherein two candidates areprepared as the number of quantization DCT coefficients in saidselecting step, one is selected among them, and a similarity betweenfirst image characteristic amount data associated with the smallernumber of quantization DCT coefficients and second image characteristicamount data associated with the greater number of quantization DCTcoefficients is judged, and one of the first image characteristic amountdata and the second image characteristic amount data is selected inaccordance with a comparison result between a similarity value and apredetermined threshold value, wherein, when the similarity between thefirst image characteristic amount data and the second imagecharacteristic amount data is judged, judgement of the similarity iseffected by supplementing a predetermined value as data of a coefficientportion which is not included in the first image characteristic amountdata having a smaller number of coefficients but is included in thesecond image characteristic amount data having a greater number ofcoefficients to the first image characteristic amount data, and whereinthe predetermined value is 16 which is the number of quantization DCTcoefficients.
 18. A computer-readable storage medium on which is storeda computer-executable program, the program comprising: program code fora DCT processing step of effecting DCT processing of an image which isrepresented by Y/Cb/Cr color space; program code for a quantization stepof effecting quantization of data subjected to the DCT processing bysaid code for a DCT processing step; program code for a judging step ofjudging whether an original image is a moving image or a still image;program code for a coefficient selecting step of selecting a number ofquantization DCT coefficients to be extracted from among thequantization DCT coefficients subjected to the quantization by said codefor a quantization step, in accordance with a judging result of saidcode for a judging step; and program code for a setting step of settingthe number of quantization DCT coefficients selected by said code for acoefficient selecting step as an image characteristic amount; whereinthe quantization DCT coefficients of Y/Cb/Cr components are re-arrangedby zigzag scanning, and, when the original image is a still image,greater than or equal to six quantization DCT coefficients of a Ycomponent and greater than or equal to three quantization DCTcoefficients of Cb/Cr components are selected, respectively, from a lowfrequency component side, and, when the original image is a movingimage, six quantization DCT coefficients of the Y component and threequantization DCT coefficients of the Cb/Cr components are selected,respectively from a low frequency component side.